speed of light in metamaterials

No, I think that speed of em wave in metamaterials like em in natural materials with the same n, but direction of em is difference

Thank, but some metamaterial have negative n which mean the light must travel faster!

No, it does not mean that at all. The "negative n" refers to Snell's law of waves incident on a media. The wave bends in a way that looks like the media has a negative n.